A vacuum chamber and chamber parts used for a chemical vapor deposition device, a physical vapor deposition device, a dry etching device, and the like are required to have corrosion resistance to a corrosive gas (hereinafter, referred to as gas corrosion resistance or resistance to gas corrosion), because a corrosive gas containing halogen elements such as chlorine, fluorine, bromine and the like are introduced into the chamber as a reactive gas, an etching gas, and a cleaning gas. In addition to the corrosive gas introduction, halogen-based plasma is generated in the chamber in many cases. Therefore, the vacuum chamber and chamber parts are also required to have corrosion resistance to plasma (hereinafter, referred to as plasma resistance).
To satisfy such requirements, conventionally, a vacuum chamber has been mainly made of stainless steel. However, a vacuum chamber made of stainless steel is heavy in weight, and therefore, requires large-scale foundation to support its construction. In addition, a vacuum chamber made of stainless steel does not have sufficient thermal conductivity, and therefore, much time is required for baking operation. There is also a problem that heavy metal such as chromium and nickel, which are alloy components of stainless steel, are released into the atmosphere during operation, resulting in spoilage the products treated in the vacuum chamber. Under such circumstances, studies have been conducted to develop a vacuum chamber and chamber parts made of aluminum or its alloys which is lighter in weight than those made of stainless steel and is excellent in thermal conductivity without the problem of heavy metal contamination.
However, without being subjected to surface treatment, a surface of aluminum or its alloys is not always excellent in resistance to gas corrosion and plasma. To give resistance to gas corrosion and plasma, any surface treatment is necessary. For this purpose, various studies have been conducted. For example, Japanese Patent Publication No. 5-53870 discloses a vacuum chamber which uses aluminum or its alloys whose surface is anodized to form an anodic oxide coating, thereby increasing gas corrosion resistance. However, no prior art, including the invention disclosed in Japanese Examined Patent Publication No. 5-53870, provides an anodic oxide coating which sufficiently serves as a protective coating against a corrosive gas and plasma. If an anodic oxide coating or a base material is corroded and damaged, products by the corrosion come out therefrom in a particle form. If a vacuum chamber or chamber part having such a coating layer or a base material is used in, for example, a semiconductor manufacturing, defective products may be produced. Accordingly, there has been a demand for improvement.
Japanese Patent publication No. 5-53871 discloses that an ion plating method is employed to form a coating (made of, for example, TiN, TiC, and the like) excellent in corrosion resistance on the surface of a vacuum chamber made of aluminum or its alloy. However, if the coating is formed by the vapor phase synthesis method such as ion plating, problems arise in that the obtained coating has small density and high cost is required for treatment. Japanese Patent Publication No. 5-53872 discloses an ion-implantation method. This method, however, is not adequate for treating a vacuum chamber or chamber part with a complicated form, and in addition, requires high cost for treatment as well as an ion plating method.
The present invention has been conducted to solve the above-described problems, and the first objective thereof is to provide a vacuum chamber or chamber part made of aluminum or its alloys excellent in resistance to gas corrosion and plasma by an economical anodizing method.
The second objective of the present invention is to provide a method for treating a surface the vacuum chamber and chamber parts.
The third objective of the present invention is to provide material used for producing the vacuum chamber and chamber parts.